1. Field of the Invention
The present invention relates to a method for producing a DDR zeolite which can be used for a catalyst, a catalyst carrier, an adsorbent, a gas separation membrane, a pervaporation membrane, and the like.
2. Description of Related Art
Zeolite includes many kinds which are called LTA, MFI, MOR, AFI, FER, FAU, and DDR into which the zeolite is classified according to a crystal structure thereof.
Of them, DDR (Deca-Dodecasil 3R) comprises a silica as a main component and has a pore which is formed by a polyhedron including an oxygen-containing eight-membered ring in a crystal structure thereof. Pore size of the DDR zeolite is 4.4×3.6 angstrom which is relatively small in pore size of a zeolite.
The DDR zeolite has a difference in adsorption properties to low molecular weight gases in addition to the small pore size. Thus, the DDR zeolite is applied to an adsorbent which separates only low molecular weight gases. For example, when forming in the membrane form, the DDR zeolite can be used as a molecular sieve membrane to low molecular weight gases.
A known method for producing a DDR zeolite includes a method in which crystals of a DDR zeolite are grown by using 1-adamantaneamine as a structure-defining agent, using a colloidal silica, ethylenediamine and water as raw materials, and adding a seed crystal of a DDR zeolite to these raw materials to carry out a hydrothermal synthesis. The production method obtains an all-silica type DDR zeolite containing no aluminium (Patent Documents 1 and 2).